After my _Address_ to our _Great Founder_ and _Patron_, I could not but think my self oblig’d, in consideration of those _many Ingagements_ you have laid upon me, to offer these my _poor Labours_ to this MOST ILLUSTRIOUS ASSEMBLY. YOU have been pleas’d formerly to accept of these rude _Draughts_. I have since added to them some _Descriptions_, and some _Conjectures_ of my own. And therefore, together with YOUR _Acceptance_, I must also beg YOUR _pardon_. The Rules YOU have prescrib’d YOUR selves in YOUR Philosophical Progress do seem the best that have ever yet been practis’d. And particularly that of avoiding _Dogmatizing_, and the _espousal_ of any _Hypothesis_ not sufficiently grounded and confirm’d by _Experiments_. This way seems the most excellent, and may preserve both _Philosophy_ and _Natural History_ from its former _Corruptions_. In saying which, I may seem to condemn my own Course in this Treatise; in which there may perhaps be some _Expressions_, which may seem more _positive_ then YOUR Prescriptions will permit: And though I desire to have them understood only as _Conjectures_ and _Quæries_ (which YOUR Method does not altogether disallow) yet if even in those I have exceeded, ’tis fit that I should declare, that it was not done by YOUR Directions. For it is most unreasonable, that YOU should undergo the _imputation_ of the _faults_ of my _Conjectures_, seeing YOU can receive so _small advantage_ of reputation by the _sleight Observations_ of YOUR most humble and most faithful Servant ROBERT HOOKE. * * * * * THE PREFACE. It is the great prerogative of Mankind above other Creatures, that we are not only able to _behold_ the works of Nature, or barely to _sustein_ our lives by them, but we have also the power of _considering_, _comparing_, _altering_, _assisting_, and _improving_ them to various uses. And as this is the peculiar priviledge of humane Nature in general, so is it capable of being so far advanced by the helps of Art, and Experience, as to make some Men excel others in their Observations, and Deductions, almost as much as they do Beasts. By the addition of such _artificial Instruments_ and _methods_, there may be, in some manner, a reparation made for the mischiefs, and imperfection, mankind has drawn upon it self, by negligence, and intemperance, and a wilful and superstitious deserting the Prescripts and Rules of Nature, whereby every man, both from a deriv’d corruption, innate and born with him, and from his breeding and converse with men, is very subject to slip into all sorts of errors.